Wobbly earth may contribute to extinction of mammals, study finds

Natural shifts in the earth’s orbit and axis correspond to the periodic emergence and extinction of rodents and likely other mammals as well, says a study published today in Nature. Researchers studying 22 million years of rodent fossil records in central Spain found that certain species experienced a slow, fading extinction roughly every million years and every 2.4 million years. The wipeouts correspond with cycles in the ellipticity of the earth’s orbit and the perpendicularity and tilt of its axis; the astronomical cycles create periods of global cooling, affecting precipitation, habitat, vegetation, and food availability. The next period of wobbly-earth-induced species turnover is likely tens of thousands of years off; at the rate we’re going, we’ll probably eliminate most species before it even gets here.